The DNeasy mericon Food Kit is designed to enable extraction of high-quality nucleic acids from a variety of raw and processed foods. The carryover of PCR inhibitors from these complex food matrices is minimized. The kit forms part of the comprehensive QIAGEN food testing portfolio, which also features assays for pathogen and GMO DNA detection and ingredient authentication. The procedure can be fully automated on the QIAcube.

The DNeasy mericon Food Kit is intended for molecular biology applications in food, animal feed, and pharmaceutical product testing. This product is not intended for the diagnosis, prevention, or treatment of a disease.

High yields of DNA and minimal inhibitor carryover.

Samples of peanut butter and chocolate were prepared using the DNeasy mericon Food Kit (standard protocol) and products from 3 other suppliers to amplify a segment of the tnrL chloroplast tRNA gene. (A) Average quantification value (Cq) is substantially lower for samples prepared with the DNeasy mericon Food Kit compared to the other suppliers. (B) Using inhibitor-free DNA, this assay gives a positive Cq shift between 2.9–3.5 when samples are diluted 1:10; lower shifts indicate the presence of inhibitors. To test for inhibitors carried over from the sample preparation procedure, samples were diluted 1:10 and the same DNA segment was amplified. Both food samples were inhibitor-free when prepared with the DNeasy mericon Food Kit. Samples prepared with products from the other suppliers showed strong inhibitor contamination.

During production, food is subjected to heat, irradiation, high pressure, and changes in pH which lead to DNA degradation and fragmentation. The optimized chemistry of the DNeasy mericon Food Kit was developed to recover short DNA fragments (down to 100 bp) ensuring that even highly fragmented DNA is efficiently isolated and subsequently amplified in PCR reactions. With these features, extraction with the DNeasy mericon Food Kit is the first universally applicable extraction method that generates optimal and reliable results even when using strongly inhibitory, highly processed, fatty, acidic, high, or low DNA content foods (see Figure "High yields of DNA and minimal inhibitor carryover" and Figure "Heightened resistance to inhibitors"). In addition, establishing multiple lysis procedures for different food matrices is no longer necessary.

The nonionic detergent CTAB is widely used for efficient extraction of total cellular nucleic acids from a wide range of tissue types. Depending on the salt conditions, CTAB may complex with cellular nucleic acids (low-salt conditions) or complex with cellular inhibitors, such as polysaccharides, proteins, and plant metabolites (high-salt conditions; as found in the Food Lysis Buffer).

With fewer workflow steps than conventional CTAB protocols, up to 30 samples can be processed in 2.5 hours (see Figure "Efficient and rapid DNA extraction"). DNA recovery with these kits is demonstrably high and efficient.

Procedure

The optimized protocols for the DNeasy mericon Food Kit use CTAB in combination with Proteinase K to first digest compact tissue and then to subsequently precipitate proteins with simultaneous precipitation of other cellular and food-derived inhibitors.

Inhibitors are precipitated by centrifugation, while the extracted DNA remains in solution. In the subsequent chloroform extraction, any remaining CTAB-protein, CTAB-debris, or CTAB-polysaccharide complex not precipitated is removed together with other lipophilic inhibitors by extraction into the organic chloroform phase. Only the aqueous phase containing the DNA and significantly depleted inhibitors is processed further. This phase is mixed with binding buffer (to adjust binding conditions) and applied to the QIAquick Spin Columns. The resulting DNA is immediately ready for use in a downstream mericon real-time PCR assay.

Applications

The DNeasy mericon Food Kit is designed for rapid (up to 30 extractions in 2.5 hours) purification of DNA from a variety of raw and processed food matrices, while minimizing the carryover of PCR inhibitors inherent to complex food samples.